Threaded pipe joint having improved seal ring entrapment

ABSTRACT

The box end of a threaded joint has an interior profile of an inwardly tapered threaded section, followed by a smooth sealing surface parallel to the longitudinal axis of the threaded joint, followed by an increased diameter seal ring groove, followed by an inwardly tapered smooth sealing surface. The pin end of the joint has an external torque shoulder, followed by an inwardly tapered threaded section, followed by a reduced diameter pipe dope reservoir, followed by an extrusion hump used to extrude a deformable seal ring used in the seal ring groove, followed by an inwardly tapered smooth sealing surface. When the threaded joint is fully made up, the entrapped seal ring has a primary metal-to-metal seal on its one side, formed by the mated smooth, tapered surfaces, and a secondary metal-to-metal seal formed by the extrusion hump and the surface above the seal ring groove.

RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.07/320,476, filed Mar. 8, 1989, now U.S. Pat. No. 4,944,538, July 31,1990.

BACKGROUND OF THE INVENTION

This invention relates generally to threaded joints, and moreparticularly to threaded connections between sections of casing, tubingor drill pipe used in oil and gas wells.

In the drilling of oil, gas and like wells, it is customary to drill tothe desired formation or formations, cement casing in place in the wellbore and provide tubing extending downwardly in the well bore from thesurface inside the casing, the annular space between the casing andtubing being packed off by a packer; although, many wells are producedwithout a packer. Ordinarily, the casing is perforated at the face ofthe formation or is set above the formation traversed by the well boreand a section of tail pipe is provided below the packer. The tail pipemay be perforated or slotted or open-ended so that, ordinarily, porefluid from the formation flows into the well bore, such as through theperforations in the casing or below the casing and into the interior ofthe well bore into tubing or casing up to the surface or is pumpedtherethrough. In some instances, the flow is in the annular spacebetween the tubing and the casing such, as for example, in the case ofdual or multiple completions where one formation is being produced inthe tubing and another formation is being produced in the annular spacebetween the tubing and the casing.

In producing oil, gas and like wells, particularly in those wells underhigh pressure, joints in the tubing sometimes fail and permit oil, gasand the like to leak through the tubing into the annular space whichprovides a high pressure on the casing at the surface, which is theweakest point of the various strings of pipe positioned in the wellbore. These leaking joints are ordinarily caused due to the failure toobtain a satisfactory seal, such as caused by normal wear and tear,improper machining and, in those joints utilizing packing, by thecorrosive action of the fluid in the well bore.

It is well known in the tubing and casing arts to use a polymerizedtetrafluoroethylene packing or sealing ring to assist in the sealing offof the high pressures encountered in oil and gas wells.

For example, U.S. Pat. No. 3,054,628, assigned to the assignee of thepresent application, shows such a ring slipped over the lower end of thepin member, and which is deformed against the tapered surface of the boxmember.

U S. Pat. No. 3,047,316, assigned to the assignee of the presentapplication, shows a seal ring engaged by the threads of the pin member,causing a portion of the seal ring to be forced into the entrancebetween the first two full height threads to seal the passage.

U.S. Pat. No. 2,980,451, assigned to the assignee of the presentapplication, shows an annular groove intermediate the thread ends oneither the pin member or the box member, with the seal member seated inthe groove. As the threads are made up, the seal member is extruded intothe threaded section adjacent the annular groove.

Although each of the foregoing prior art designs has enjoyedconsiderable commercial success, there has arisen the need for moreuniform sealing when extruding the seal ring. The designs using the sealentrapped within the threads, in particular, sometimes experiencenon-uniform extrusion, and, thus, non-uniform sealing.

These same designs having the seal ring extruding into the threads alsohave had only a single metal-to-metal seal on one end of the entrappedseal, with the thread form on the other end of the entrapped seal ring.

It is therefore the primary object of the present invention to provide anew and improved threaded pipe joint having improved uniformity of sealring entrapment.

It is yet another object of the present invention to provide a new andimproved threaded pipe joint having the extruded seal ring completelyentrapped by two metal-to-metal seals.

It is still another object of the invention to provide a new andimproved threaded pipe joint which includes engagement means designed todecrease the likelihood of seal damage during makeup of the threadedjoint.

SUMMARY OF THE INVENTION

The primary object of the invention is accomplished, generally, by theprovision of a box member having an inwardly tapered threaded section onits inner periphery and an enlarged diameter, seal ring entrapment areabelow said inwardly tapered threaded section, a deformable seal ring insaid entrapment area, a pin member having an inwardly tapered threadedsection on its outer periphery adapted to threadably engage the threadedsection of said box member, and having an enlarged diameter, extrusionhump sized to engage and deform the deformable seal ring, therebycreating a uniform, high pressure seal between the box member and thepin member.

Another object of the invention is accomplished, generally, by theprovision of the extrusion hump being sized to provide a firstmetal-to-metal seal on one side of the entrapped seal, while the primarymetal-to-metal seal is located on the other side of the entrapped seal.

Yet another object of the invention is accomplished, generally, by theextrusion hump being sized to contact the inner periphery of the boxmember prior to the engagement of the primary metal-to-metal seal,thereby aligning the primary metal-to-metal sealing surfaces anddecreasing the aspect of seal damage otherwise resulting frommisalignment.

These and other objects, features and advantages will become apparentfrom the following detailed description taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevated view, partly in cross-section, of a madeupthreaded joint according to the present invention.

FIG. 2 is an elevated, exploded view, partly in cross-section, of a pinmember, deformable seal ring and box member according to the presentinvention, prior to the makeup of the threaded joint.

FIG. 3 is an elevated, cross-sectional view of the pin member an boxmember according to the present invention, during makeup of the threadedconnection but prior to the extrusion hump first contacting thedeformable seal member.

FIG. 4 is an elevated, cross-sectional view of the pin and box membersof FIG. 3, during makeup of the threaded connection shortly after theextrusion hump first contacts the deformable seal member.

FIG. 5 is an elevated, cross-sectional view of the pin and box of FIG.3, wherein the extrusion hump has completed the extrusion of thedeformable seal member in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings in more detail, especially to FIG. 1,there is illustrated an elevational view, partly in cross-section, of athreaded joint 10 according to the present invention, comprised of a pinmember 11 and a box member 12. The pin member 11 has an extrusion hump13 which has caused the deformable seal ring 14 to be deformed into asealing arrangement between the pin member 11 and the box member 12, allof which is described in greater detail hereinafter.

Referring now to FIG. 2, the pin member 11 of FIG. 1 is illustrated anddescribed in greater detail. The pin member 11 includes an inwardlytapered thread 20 on its outer periphery having a reduced diametersection 21 below the end of the thread 20 which is used as a dopereservoir. Immediately adjacent the dope reservoir 21 is an extrusionhump 22 having an increased diameter as compared to the diameter of thedope reservoir 21. Immediately below the extrusion hump 22 is a pin end23 whose outer surface serves as the primary metal-to-metal seal whenengaged with the surface 33 of box member 12.

FIG. 2 also illustrates a deformable seal ring 25 which is formed, in apreferred embodiment, of polymerized tetrafluoroethylene. Themanufacturer of this material is E.I. DuPont Nemours and Co. under thetrade name "Teflon".

Referring further to FIG. 2, the box member 12 is illustrated in greaterdetail. The box member 12 has an inwardly tapered thread 30 on its innerperiphery designed to match the thread 20 on the outer periphery of thepin member 11. Immediately below the lower end of the threaded section30 is a smooth surface 31 sized and positioned to form a secondarymetal-to-metal seal with the outer surface 26 of the extrusion hump 22.Below the surface 31 of the inner periphery of the box member 12 is anenlarged diameter section 32 for retaining the deformable seal member 25as is illustrated in greater detail in FIG. 3 hereinafter. Still furtherbelow the sealing ring retention portion 32 is a smooth surface 33 whichforms the primary metal-to-metal seal when engaged with the surface ofthe lower pin member 23.

Referring now to FIG. 3, the pin member 11 is illustrated as beingpartially madeup with the box member 12 such that the threaded section20 of the pin member 11 has engaged some of the threads 30 of the boxmember 12. As illustrated, the extrusion hump 22 at this stage in themakeup process has engaged the sealing surface 31, but has yet to engagethe deformable sealing ring 25. At this point in the process, thesurface of pin end 23 and surface 33 have not yet engaged to form theprimary metal-to-metal seal. The manufacturing process in accordancewith the preferred embodiment of the present invention contemplates theextrusion hump 22 being machined on an axis parallel to the longitudinalaxis of the threaded joint while the primary metal-to-metal seal ismachined on a taper to the longitudinal axis of the threaded joint. Bymachining the extrusion hump parallel to the threaded joint axis, thisnecessarily allows the extrusion hump 22 to make contact with thesurface 31 before the primary metal-to-metal surfaces are engaged. Thisthen allows the primary metal-to-metal surfaces to be guided togetherwithout damage which can occur due to misalignment of the pin memberwith the box member. By having the extrusion hump 22 contact the surface31 prior to the primary metal-to-metal surfaces coming together, thereis a decrease of the probability of high angle cocking of the pin member11. As another way of expressing this relationship, the initial contactof the extrusion hump 22 with the surface 31 does not prevent cocking ofthe pin member, but lessens the angle of cocking to thus reduce theprobability of damage to the primary metal-to-metal seal. If it were notfor this feature, the pin member 11 can easily become cooked such thatthe point 28 of the pin member can dig into the surface 33 and causedamage to the seal.

Referring now to FIG. 4, following additional makeup of the joint, theextrusion hump 22 is illustrated as having now contacted the seal ring25 which causes a partial deformation of the seal ring 25.

FIG. 5 illustrates the complete makeup of the threaded joint such thatthe seal ring 25 is completely deformed in accordance with the presentinvention and the primary metal-to-metal sealing surfaces 23, 33 areengaged. It should also be appreciated that the surface 26 of extrusionhump 22 forms a secondary metal-to-metal seal with the surface 31 of thebox member. Thus, there is a primary metal-to-metal seal on one side ofthe deformed seal ring 25 and a secondary metal-to-metal seal on theupper side of the deformed seal ring 25.

In order to improve the control of the machining of the seal ringentrapment area 32, the extrusion hump 22 and the seal ring retentiongroove 32, with its two adjacent sealing surfaces 31, 33, are machinedwith the same tool. Although the dimensions will vary with differentsize casing, tubing, drill pipe, or the like, in a 5" casing made inaccordance with the present invention, the dope reservoir 21 is cut to adiameter of 4.264". The extrusion hump 22 is cut to a diameter of 4.362"and has a length between points 53 and 54, as illustrated in FIG. 3, of0.300". The seal ring groove 32 has a diameter of 4.402" and has alength between points 50 and 51, also illustrated in FIG. 3, of 0.250".The surface 31, also machined parallel to the longitudinal axis of thethreaded joint, has a diameter of 4.356". Thus, the extrusion hump 22,with its diameter of 4.362", forms an interference fit with the surface31, helping to prevent cocking of the pin member 11. The surface 33,having a length of 0.400", has a taper of 1-1/8" per foot and has adiameter at point 52 of 4.244". The surface of pin end 23 has a matchingtaper.

The groove 21 above the extrusion hump 22, having a reduced diameter,acts as a reservoir to allow entrapped thread lubricants to flowtherein. In typical prior art threaded connections, the threadlubricants would be trapped between the external torque shoulder and theprimary metal-to-metal seal with no place to flow, resulting in anincrease of the stresses in the connection.

Referring again to FIG. 1, it should be appreciated that in thepreferred embodiment of the present invention, the torque shoulder iscomprised of the upper surface 15 of the box member 12 being torquedagainst the shoulder 16 of the pin member. As an alternative embodiment,if desired, the lower end 17 of pin member 11 can be torqued against theshoulder 18 within the interior of the box member 12.

In view of the foregoing, it will be seen that by this invention athreaded joint has been produced which has greatly improved sealingcharacteristics for operations in high pressure oil and gas wells, orthe like. The features of this invention can be used with casing,tubing, drill pipe, and the like, although the preferred embodimentcontemplates manufacture and utilization of well casing.

What is claimed is:
 1. A pin member for use with a box member to form athreaded, sealed joint, said box member having an inwardly taperedthreaded section and a sealing groove below a lower end of its threadedsection and a deformable seal ring in said seal ring groove, said pinmember comprising;a tool joint member having an inwardly taperedthreaded section on its outer periphery, an extrusion hump having agiven diameter below the end of said threaded section for entrappingsaid seal ring to form a seal, said pin member having an area betweenthe lower end of said threaded section and the extrusion hump of adiameter less than the said given diameter of said extrusion hump and afirst smooth, inwardly tapered surface on said outer periphery below andimmediately adjacent to said extrusion hump having its greatest diameterless than the said given diameter of said extrusion hump.
 2. The pinmember as defined in claim 1, wherein the area between the lower end ofthe threaded section and the extrusion hump is adjoining the extrusionhump.